1. Field of the Invention
The present invention relates to a composite structure useful as an artificial implant material such as artificial dental roots, artifical bones and the like.
2. Description of the Prior art
Materials for artificial bones must have good affinity with vital tissues, must easily, chemically bond to natural bones and must have good mechanical properties.
A sintered apatite body is known as material for aritificial bones. It is made in the following way. First, calcium carbonate powder is heated. An aqueous solution of phosphoric acid is then added to the heated powder, thus preparing apatite powder. The apatite powder is press-formed and sintered, providing the sintered body. The body has good affinity with vital tissues and excellent chemical bondability with natural bones. Its mechanical properties can be improved to some extent by special treatments. The body, however, does not have a sufficient mechanical strength.
Alumina (sapphire) is also used as material for artificial bones. It has a good affinity with vital tissues and a great mechanical strength, but cannot chemically bond to natural bones. To compensate for the bondability of alumina, holes or concaves are cut in an alumina body, and some portions of a natural bone are forcibly fitted in these holes or concaves, whereby the bones is fastened to the alumina body. However, the joint between the bone and the alumina body tends to loosen when the bone shrinks or deforms with lapse of time.
Na.sub.2 O--CaO--SiO.sub.2 --P.sub.2 O.sub.5 system glass and Na.sub.2 O--K.sub.2 O--MgO--CaO--SiO.sub.2 --P.sub.2 O.sub.5 (CaF.sub.2) system glass ceramics have good affinity with vital tissues and can chemically bond to natural bones. Their mechanical properties are, however, poor.
Various ceramic materials exhibiting good affinity with vital tissues, excellent bondability to natural bones and sufficient mechanical strength are now being researched. The data presented in the 15th Lecture on Ceramics (Bio-ceramics), 1984discloses that zirconia has good affinity with vital tissues. Also, Japanese Patent Disclosure No. 59-112908 discloses some materials for artificial bones.